{
    "mode": "man",
    "parameter": "co",
    "section": "1",
    "url": "https://www.chedong.com/phpMan.php/man/co/1/json",
    "generated": "2026-06-02T20:22:00Z",
    "synopsis": "co [options] file ...",
    "sections": {
        "NAME": {
            "content": "co - check out RCS revisions\n",
            "subsections": []
        },
        "SYNOPSIS": {
            "content": "co [options] file ...\n",
            "subsections": []
        },
        "DESCRIPTION": {
            "content": "co retrieves a revision from each RCS file and stores it into the corresponding working file.\n\nFilenames  matching  an  RCS suffix denote RCS files; all others denote working files.  Names\nare paired as explained in ci(1).\n\nRevisions of an RCS file can be checked out locked or unlocked.  Locking a revision  prevents\noverlapping updates.  A revision checked out for reading or processing (e.g., compiling) need\nnot be locked.  A revision checked out for editing and later checkin must normally be locked.\nCheckout  with locking fails if the revision to be checked out is currently locked by another\nuser.  (A lock can be broken with rcs(1).)  Checkout with locking also requires the caller to\nbe  on  the access list of the RCS file, unless he is the owner of the file or the superuser,\nor the access list is empty.  Checkout without locking is not subject to accesslist  restric‐\ntions, and is not affected by the presence of locks.\n\nA  revision  is selected by options for revision or branch number, checkin date/time, author,\nor state.  When the selection options are applied in combination, co retrieves the latest re‐\nvision  that  satisfies  all  of them.  If none of the selection options is specified, co re‐\ntrieves the latest revision on the default branch (normally the trunk, see the -b  option  of\nrcs(1)).   A  revision or branch number can be attached to any of the options -f, -I, -l, -M,",
            "subsections": [
                {
                    "name": "-p -q -r -u -d -s -w",
                    "content": "branch,  the selected branch, which is either specified by one of -f, ..., -u, or the default\nbranch.\n\nA co command applied to an RCS file with no revisions creates a zero-length working file.  co\nalways performs keyword substitution (see below).\n",
                    "flag": "-w"
                }
            ]
        },
        "OPTIONS": {
            "content": "",
            "subsections": [
                {
                    "name": "-r",
                    "content": "retrieves the latest revision whose number is less than or equal to rev.  If rev indi‐\ncates a branch rather than a revision, the latest  revision  on  that  branch  is  re‐\ntrieved.  If rev is omitted, the latest revision on the default branch (see the -b op‐\ntion of rcs(1)) is retrieved.  If rev is $, co determines  the  revision  number  from\nkeyword  values in the working file.  Otherwise, a revision is composed of one or more\nnumeric or symbolic fields separated by periods.  If rev begins with  a  period,  then\nthe default branch (normally the trunk) is prepended to it.  If rev is a branch number\nfollowed by a period, then the latest revision on that branch is  used.   The  numeric\nequivalent  of  a symbolic field is specified with the -n option of the commands ci(1)\nand rcs(1).\n",
                    "flag": "-r"
                },
                {
                    "name": "-l",
                    "content": "same as -r, except that it also locks the retrieved revision for the caller.\n",
                    "flag": "-l"
                },
                {
                    "name": "-u",
                    "content": "same as -r, except that it unlocks the retrieved revision if  it  was  locked  by  the\ncaller.   If  rev is omitted, -u retrieves the revision locked by the caller, if there\nis one; otherwise, it retrieves the latest revision on the default branch.\n",
                    "flag": "-u"
                },
                {
                    "name": "-f",
                    "content": "forces the overwriting of the working file; useful in connection with  -q.   See  also\nFILE MODES below.\n",
                    "flag": "-f"
                },
                {
                    "name": "-kkv",
                    "content": "vision keyword.  A locker's name is inserted in the  value  of  the  Header,  Id,  and\nLocker  keyword strings only as a file is being locked, i.e. by ci -l and co -l.  This\nis the default.\n"
                },
                {
                    "name": "-kkvl -kkv",
                    "content": "currently locked.\n"
                },
                {
                    "name": "-kk",
                    "content": "STITUTION below.  For example, for the Revision keyword, generate  the  string  $Revi‐‐\nsion$ instead of $Revision: 5.10.1 $.  This option is useful to ignore differences due\nto keyword substitution when comparing different revisions of a  file.   Log  messages\nare  inserted  after  $Log$  keywords even if -kk is specified, since this tends to be\nmore useful when merging changes.\n"
                },
                {
                    "name": "-ko",
                    "content": "checked in.  For example, for the Revision keyword, generate the string $Revision: 1.1\n$ instead of $Revision: 5.10.1 $ if that is how the string appeared when the file  was\nchecked  in.   This can be useful for file formats that cannot tolerate any changes to\nsubstrings that happen to take the form of keyword strings.\n"
                },
                {
                    "name": "-kb -ko",
                    "content": "forms  all working file input and output in binary mode.  This makes little difference\non Posix and Unix hosts, but on DOS-like hosts one should use rcs -i -kb to initialize\nan  RCS  file  intended  to be used for binary files.  Also, on all hosts, rcsmerge(1)\nnormally refuses to merge files when -kb is in effect.\n"
                },
                {
                    "name": "-kv",
                    "content": "word, generate the string 5.10.1 instead of $Revision: 5.10.1 $.  This can help gener‐\nate files in programming languages where it is hard to strip keyword  delimiters  like\n$Revision: $ from a string.  However, further keyword substitution cannot be performed\nonce the keyword names are removed, so this option should be used with care.   Because\nof  this  danger  of  losing keywords, this option cannot be combined with -l, and the\nowner write permission of the working file is turned off;  to  edit  the  file  later,\ncheck it out again without -kv.\n"
                },
                {
                    "name": "-p",
                    "content": "prints  the  retrieved  revision  on the standard output rather than storing it in the\nworking file.  This option is useful when co is part of a pipe.\n",
                    "flag": "-p"
                },
                {
                    "name": "-q",
                    "content": "quiet mode; diagnostics are not printed.\n",
                    "flag": "-q"
                },
                {
                    "name": "-I",
                    "content": "interactive mode; the user is prompted and questioned even if the  standard  input  is\nnot a terminal.\n",
                    "flag": "-I"
                },
                {
                    "name": "-d",
                    "content": "than or equal to date.  The date and time can be given in free format.  The time  zone\nLT  stands  for local time; other common time zone names are understood.  For example,\nthe following dates are equivalent if local time is  January  11,  1990,  8pm  Pacific\nStandard Time, eight hours west of Coordinated Universal Time (UTC):\n\n8:00 pm lt\n4:00 AM, Jan. 12, 1990           default is UTC\n1990-01-12 04:00:00+00           ISO 8601 (UTC)\n1990-01-11 20:00:00-08           ISO 8601 (local time)\n1990/01/12 04:00:00              traditional RCS format\nThu Jan 11 20:00:00 1990 LT      output of ctime(3) + LT\nThu Jan 11 20:00:00 PST 1990     output of date(1)\nFri Jan 12 04:00:00 GMT 1990\nThu, 11 Jan 1990 20:00:00 -0800  Internet RFC 822\n12-January-1990, 04:00 WET\n\nMost  fields in the date and time can be defaulted.  The default time zone is normally\nUTC, but this can be overridden by the -z option.  The other defaults  are  determined\nin  the  order year, month, day, hour, minute, and second (most to least significant).\nAt least one of these fields must be provided.  For omitted fields that are of  higher\nsignificance  than  the highest provided field, the time zone's current values are as‐\nsumed.  For all other omitted fields, the lowest possible values are assumed.  For ex‐\nample,  without -z, the date 20, 10:30 defaults to 10:30:00 UTC of the 20th of the UTC\ntime zone's current month and year.  The date/time must be quoted if it contains  spa‐\nces.\n",
                    "flag": "-d"
                },
                {
                    "name": "-M",
                    "content": "Set  the modification time on the new working file to be the date of the retrieved re‐\nvision.  Use this option with care; it can confuse make(1).\n",
                    "flag": "-M"
                },
                {
                    "name": "-s",
                    "content": "retrieves the latest revision on the selected branch whose state is set to state.\n",
                    "flag": "-s"
                },
                {
                    "name": "-S",
                    "content": "exists.  Effectively, this means the user cannot check out the same revision twice.\n",
                    "flag": "-S"
                },
                {
                    "name": "-T",
                    "content": "lock is added or removed.  This option can suppress extensive recompilation caused  by\na make(1) dependency of some other copy of the working file on the RCS file.  Use this\noption with care; it can suppress recompilation even when it is needed, i.e. when  the\nchange of lock would mean a change to keyword strings in the other working file.\n",
                    "flag": "-T"
                },
                {
                    "name": "-w",
                    "content": "retrieves  the latest revision on the selected branch which was checked in by the user\nwith login name login.  If the argument login is omitted, the caller's  login  is  as‐\nsumed.\n",
                    "flag": "-w"
                },
                {
                    "name": "-j",
                    "content": "generates  a new revision which is the join of the revisions on joinlist.  This option\nis largely obsoleted by rcsmerge(1) but is retained for backwards compatibility.\n\nThe joinlist is a comma-separated list of pairs of the form rev2:rev3, where rev2  and\nrev3  are (symbolic or numeric) revision numbers.  For the initial such pair, rev1 de‐\nnotes the revision selected by the above options -f, ..., -w.  For  all  other  pairs,\nrev1  denotes  the  revision generated by the previous pair.  (Thus, the output of one\njoin becomes the input to the next.)\n\nFor each pair, co joins revisions rev1 and rev3 with respect to rev2.  This means that\nall changes that transform rev2 into rev1 are applied to a copy of rev3.  This is par‐\nticularly useful if rev1 and rev3 are the ends of two branches that  have  rev2  as  a\ncommon  ancestor.  If rev1<rev2<rev3 on the same branch, joining generates a new revi‐\nsion which is like rev3, but with all changes that lead from rev1 to rev2 undone.   If\nchanges  from rev2 to rev1 overlap with changes from rev2 to rev3, co reports overlaps\nas described in merge(1).\n\nFor the initial pair, rev2 can be omitted.  The default is the  common  ancestor.   If\nany of the arguments indicate branches, the latest revisions on those branches are as‐\nsumed.  The options -l and -u lock or unlock rev1.\n",
                    "flag": "-j"
                },
                {
                    "name": "-V",
                    "content": "",
                    "flag": "-V"
                },
                {
                    "name": "-V",
                    "content": "ing RCS files with others who are running older versions of RCS.  To see which version\nof RCS your correspondents are running, have them invoke rcs -V; this works with newer\nversions of RCS.  If it doesn't work, have them invoke rlog on an RCS file; if none of\nthe first few lines of output contain the string branch:  it  is  version  3;  if  the\ndates'  years  have  just two digits, it is version 4; otherwise, it is version 5.  An\nRCS file generated while emulating version 3 loses its default branch.  An  RCS  revi‐\nsion generated while emulating version 4 or earlier has a time stamp that is off by up\nto 13 hours.  A revision extracted while emulating version 4 or earlier  contains  ab‐\nbreviated  dates  of  the form yy/mm/dd and can also contain different white space and\nline prefixes in the substitution for $Log$.\n",
                    "flag": "-V"
                },
                {
                    "name": "-x",
                    "content": "Use suffixes to characterize RCS files.  See ci(1) for details.\n",
                    "flag": "-x"
                },
                {
                    "name": "-z",
                    "content": "time zone for date in the -ddate option.  The zone should be empty, a numeric UTC off‐\nset, or the special string LT for local time.  The default is  an  empty  zone,  which\nuses  the  traditional  RCS  format  of  UTC without any time zone indication and with\nslashes separating the parts of the date; otherwise, times are output in ISO 8601 for‐\nmat  with  time  zone indication.  For example, if local time is January 11, 1990, 8pm\nPacific Standard Time, eight hours west of UTC, then the time is output as follows:\n\noption    time output",
                    "flag": "-z"
                },
                {
                    "name": "-z        1990/01/12 04:00:00        _(default)",
                    "content": "-zLT      1990-01-11 20:00:00-08\n-z+05:30  1990-01-12 09:30:00+05:30\n\nThe -z option does not affect dates stored in RCS files, which are always UTC.\n",
                    "flag": "-z"
                }
            ]
        },
        "KEYWORD SUBSTITUTION": {
            "content": "Strings of the form $keyword$ and $keyword:...$  embedded  in  the  text  are  replaced  with\nstrings of the form $keyword:value$ where keyword and value are pairs listed below.  Keywords\ncan be embedded in literal strings or comments to identify a revision.\n\nInitially, the user enters strings of the form $keyword$.  On  checkout,  co  replaces  these\nstrings  with  strings  of the form $keyword:value$.  If a revision containing strings of the\nlatter form is checked back in, the value fields will be replaced during the  next  checkout.\nThus,  the keyword values are automatically updated on checkout.  This automatic substitution\ncan be modified by the -k options.\n\nKeywords and their corresponding values:\n",
            "subsections": [
                {
                    "name": "$Author$",
                    "content": "The login name of the user who checked in the revision.\n\n$Date$ The date and time the revision was checked in.  With -zzone a numeric time zone offset\nis appended; otherwise, the date is UTC.\n"
                },
                {
                    "name": "$Header$",
                    "content": "A standard header containing the full RCS file name, the revision number, the date and\ntime, the author, the state, and the locker (if locked).  With -zzone a  numeric  time\nzone offset is appended to the date; otherwise, the date is UTC.\n\n$Id$   Same as $Header$, except that the RCS file name is without the directory components.\n"
                },
                {
                    "name": "$Locker$",
                    "content": "The login name of the user who locked the revision (empty if not locked).\n\n$Log$  The  log message supplied during checkin, preceded by a header containing the RCS file\nname, the revision number, the author, and the date and time.  With -zzone  a  numeric\ntime  zone  offset is appended; otherwise, the date is UTC.  Existing log messages are\nnot replaced.  Instead, the new log message is inserted after $Log:...$.  This is use‐\nful for accumulating a complete change log in a source file.\n\nEach  inserted line is prefixed by the string that prefixes the $Log$ line.  For exam‐\nple, if the $Log$ line is “// $Log: tan.cc $”, RCS prefixes each line of the log  with\n“// ”.   This  is  useful  for languages with comments that go to the end of the line.\nThe convention for other languages is to use a “ ∗∗ ” prefix inside  a  multiline  com‐\nment.   For  example,  the initial log comment of a C program conventionally is of the\nfollowing form:\n\n/∗∗\n∗∗ $Log$\n∗∗/\n\nFor backwards compatibility with older versions of RCS, if the log prefix is /∗∗ or  (∗∗\nsurrounded by optional white space, inserted log lines contain a space instead of / or\n(; however, this usage is obsolescent and should not be relied on.\n\n$Name$ The symbolic name used to check out the revision, if any.  For example, co -rJoe  gen‐\nerates $Name: Joe $.  Plain co generates just $Name:  $.\n"
                },
                {
                    "name": "$RCSfile$",
                    "content": "The RCS file name without directory components.\n"
                },
                {
                    "name": "$Revision$",
                    "content": "The revision number assigned to the revision.\n"
                },
                {
                    "name": "$Source$",
                    "content": "The full RCS file name.\n"
                },
                {
                    "name": "$State$",
                    "content": "The state assigned to the revision with the -s option of rcs(1) or ci(1).\n\nThe  following  characters in keyword values are represented by escape sequences to keep key‐\nword strings well-formed.\n\nchar     escape sequence\ntab      \\t\nnewline  \\n\nspace    \\040\n$        \\044\n\\        \\\\\n"
                }
            ]
        },
        "FILE MODES": {
            "content": "The working file inherits the read and execute permissions from the RCS file.   In  addition,\nthe  owner  write  permission  is turned on, unless -kv is set or the file is checked out un‐\nlocked and locking is set to strict (see rcs(1)).\n\nIf a file with the name of the working file exists  already  and  has  write  permission,  co\naborts  the  checkout,  asking  beforehand  if possible.  If the existing working file is not\nwritable or -f is given, the working file is deleted without asking.\n",
            "subsections": []
        },
        "FILES": {
            "content": "co accesses files much as ci(1) does, except that it does not need to read the  working  file\nunless a revision number of $ is specified.\n",
            "subsections": []
        },
        "ENVIRONMENT": {
            "content": "RCSINIT\nOptions prepended to the argument list, separated by spaces.  A backslash escapes spa‐\nces within an option.  The RCSINIT options are prepended to the argument lists of most\nRCS commands.  Useful RCSINIT options include -q, -V, -x, and -z.\n\nRCSMEMLIMIT\nNormally,  for  speed,  commands either memory map or copy into memory the RCS file if\nits size is less than the memory-limit, currently defaulting to ``unlimited''.  Other‐\nwise  (or  if  the  initially-tried speedy ways fail), the commands fall back to using\nstandard i/o routines.  You can adjust the memory limit by setting RCSMEMLIMIT to  a\nnumeric  value lim (measured in kilobytes).  An empty value is silently ignored.  As a\nside effect, specifying RCSMEMLIMIT inhibits fall-back to slower routines.\n\nTMPDIR Name of the temporary directory.  If not set, the environment variables TMP  and  TEMP\nare  inspected  instead and the first value found is taken; if none of them are set, a\nhost-dependent default is used, typically /tmp.\n",
            "subsections": []
        },
        "DIAGNOSTICS": {
            "content": "The RCS file name, the working file name, and the revision number retrieved  are  written  to\nthe  diagnostic  output.  The exit status is zero if and only if all operations were success‐\nful.\n",
            "subsections": []
        },
        "IDENTIFICATION": {
            "content": "Author: Walter F. Tichy.\nManual Page Revision: 5.10.1; Release Date: 2022-02-19.\nCopyright © 2010-2022 Thien-Thi Nguyen.\nCopyright © 1990, 1991, 1992, 1993, 1994, 1995 Paul Eggert.\nCopyright © 1982, 1988, 1989 Walter F. Tichy.\n",
            "subsections": []
        },
        "SEE ALSO": {
            "content": "ci(1), ctime(3), date(1), ident(1), make(1), rcs(1),  rcsclean(1),  rcsdiff(1),  rcsmerge(1),\nrlog(1), rcsfile(5).\n\nWalter  F.  Tichy,  RCS--A  System for Version Control, Software--Practice & Experience 15, 7\n(July 1985), 637-654.\n\nThe full documentation for RCS is maintained as a Texinfo manual.  If  the  info(1)  and  RCS\nprograms are properly installed at your site, the command\n\ninfo rcs\n\nshould give you access to the complete manual.  Additionally, the RCS homepage:\n\nhttp://www.gnu.org/software/rcs/\n\nhas news and links to the latest release, development site, etc.\n",
            "subsections": []
        },
        "LIMITS": {
            "content": "Links to the RCS and working files are not preserved.\n\nThere  is  no  way  to selectively suppress the expansion of keywords, except by writing them\ndifferently.  In nroff and troff, this is done by embedding the null-character  \\&  into  the\nkeyword.\n\n\n\nGNU RCS 5.10.1                               2022-02-19                                        CO(1)",
            "subsections": []
        }
    },
    "summary": "co - check out RCS revisions",
    "flags": [
        {
            "flag": "-r",
            "long": null,
            "arg": null,
            "description": "retrieves the latest revision whose number is less than or equal to rev. If rev indi‐ cates a branch rather than a revision, the latest revision on that branch is re‐ trieved. If rev is omitted, the latest revision on the default branch (see the -b op‐ tion of rcs(1)) is retrieved. If rev is $, co determines the revision number from keyword values in the working file. Otherwise, a revision is composed of one or more numeric or symbolic fields separated by periods. If rev begins with a period, then the default branch (normally the trunk) is prepended to it. If rev is a branch number followed by a period, then the latest revision on that branch is used. The numeric equivalent of a symbolic field is specified with the -n option of the commands ci(1) and rcs(1)."
        },
        {
            "flag": "-l",
            "long": null,
            "arg": null,
            "description": "same as -r, except that it also locks the retrieved revision for the caller."
        },
        {
            "flag": "-u",
            "long": null,
            "arg": null,
            "description": "same as -r, except that it unlocks the retrieved revision if it was locked by the caller. If rev is omitted, -u retrieves the revision locked by the caller, if there is one; otherwise, it retrieves the latest revision on the default branch."
        },
        {
            "flag": "-f",
            "long": null,
            "arg": null,
            "description": "forces the overwriting of the working file; useful in connection with -q. See also FILE MODES below."
        },
        {
            "flag": "",
            "long": null,
            "arg": null,
            "description": "vision keyword. A locker's name is inserted in the value of the Header, Id, and Locker keyword strings only as a file is being locked, i.e. by ci -l and co -l. This is the default."
        },
        {
            "flag": "",
            "long": null,
            "arg": null,
            "description": "currently locked."
        },
        {
            "flag": "",
            "long": null,
            "arg": null,
            "description": "STITUTION below. For example, for the Revision keyword, generate the string $Revi‐‐ sion$ instead of $Revision: 5.10.1 $. This option is useful to ignore differences due to keyword substitution when comparing different revisions of a file. Log messages are inserted after $Log$ keywords even if -kk is specified, since this tends to be more useful when merging changes."
        },
        {
            "flag": "",
            "long": null,
            "arg": null,
            "description": "checked in. For example, for the Revision keyword, generate the string $Revision: 1.1 $ instead of $Revision: 5.10.1 $ if that is how the string appeared when the file was checked in. This can be useful for file formats that cannot tolerate any changes to substrings that happen to take the form of keyword strings."
        },
        {
            "flag": "",
            "long": null,
            "arg": null,
            "description": "forms all working file input and output in binary mode. This makes little difference on Posix and Unix hosts, but on DOS-like hosts one should use rcs -i -kb to initialize an RCS file intended to be used for binary files. Also, on all hosts, rcsmerge(1) normally refuses to merge files when -kb is in effect."
        },
        {
            "flag": "",
            "long": null,
            "arg": null,
            "description": "word, generate the string 5.10.1 instead of $Revision: 5.10.1 $. This can help gener‐ ate files in programming languages where it is hard to strip keyword delimiters like $Revision: $ from a string. However, further keyword substitution cannot be performed once the keyword names are removed, so this option should be used with care. Because of this danger of losing keywords, this option cannot be combined with -l, and the owner write permission of the working file is turned off; to edit the file later, check it out again without -kv."
        },
        {
            "flag": "-p",
            "long": null,
            "arg": null,
            "description": "prints the retrieved revision on the standard output rather than storing it in the working file. This option is useful when co is part of a pipe."
        },
        {
            "flag": "-q",
            "long": null,
            "arg": null,
            "description": "quiet mode; diagnostics are not printed."
        },
        {
            "flag": "-I",
            "long": null,
            "arg": null,
            "description": "interactive mode; the user is prompted and questioned even if the standard input is not a terminal."
        },
        {
            "flag": "-d",
            "long": null,
            "arg": null,
            "description": "than or equal to date. The date and time can be given in free format. The time zone LT stands for local time; other common time zone names are understood. For example, the following dates are equivalent if local time is January 11, 1990, 8pm Pacific Standard Time, eight hours west of Coordinated Universal Time (UTC): 8:00 pm lt 4:00 AM, Jan. 12, 1990 default is UTC 1990-01-12 04:00:00+00 ISO 8601 (UTC) 1990-01-11 20:00:00-08 ISO 8601 (local time) 1990/01/12 04:00:00 traditional RCS format Thu Jan 11 20:00:00 1990 LT output of ctime(3) + LT Thu Jan 11 20:00:00 PST 1990 output of date(1) Fri Jan 12 04:00:00 GMT 1990 Thu, 11 Jan 1990 20:00:00 -0800 Internet RFC 822 12-January-1990, 04:00 WET Most fields in the date and time can be defaulted. The default time zone is normally UTC, but this can be overridden by the -z option. The other defaults are determined in the order year, month, day, hour, minute, and second (most to least significant). At least one of these fields must be provided. For omitted fields that are of higher significance than the highest provided field, the time zone's current values are as‐ sumed. For all other omitted fields, the lowest possible values are assumed. For ex‐ ample, without -z, the date 20, 10:30 defaults to 10:30:00 UTC of the 20th of the UTC time zone's current month and year. The date/time must be quoted if it contains spa‐ ces."
        },
        {
            "flag": "-M",
            "long": null,
            "arg": null,
            "description": "Set the modification time on the new working file to be the date of the retrieved re‐ vision. Use this option with care; it can confuse make(1)."
        },
        {
            "flag": "-s",
            "long": null,
            "arg": null,
            "description": "retrieves the latest revision on the selected branch whose state is set to state."
        },
        {
            "flag": "-S",
            "long": null,
            "arg": null,
            "description": "exists. Effectively, this means the user cannot check out the same revision twice."
        },
        {
            "flag": "-T",
            "long": null,
            "arg": null,
            "description": "lock is added or removed. This option can suppress extensive recompilation caused by a make(1) dependency of some other copy of the working file on the RCS file. Use this option with care; it can suppress recompilation even when it is needed, i.e. when the change of lock would mean a change to keyword strings in the other working file."
        },
        {
            "flag": "-w",
            "long": null,
            "arg": null,
            "description": "retrieves the latest revision on the selected branch which was checked in by the user with login name login. If the argument login is omitted, the caller's login is as‐ sumed."
        },
        {
            "flag": "-j",
            "long": null,
            "arg": null,
            "description": "generates a new revision which is the join of the revisions on joinlist. This option is largely obsoleted by rcsmerge(1) but is retained for backwards compatibility. The joinlist is a comma-separated list of pairs of the form rev2:rev3, where rev2 and rev3 are (symbolic or numeric) revision numbers. For the initial such pair, rev1 de‐ notes the revision selected by the above options -f, ..., -w. For all other pairs, rev1 denotes the revision generated by the previous pair. (Thus, the output of one join becomes the input to the next.) For each pair, co joins revisions rev1 and rev3 with respect to rev2. This means that all changes that transform rev2 into rev1 are applied to a copy of rev3. This is par‐ ticularly useful if rev1 and rev3 are the ends of two branches that have rev2 as a common ancestor. If rev1<rev2<rev3 on the same branch, joining generates a new revi‐ sion which is like rev3, but with all changes that lead from rev1 to rev2 undone. If changes from rev2 to rev1 overlap with changes from rev2 to rev3, co reports overlaps as described in merge(1). For the initial pair, rev2 can be omitted. The default is the common ancestor. If any of the arguments indicate branches, the latest revisions on those branches are as‐ sumed. The options -l and -u lock or unlock rev1."
        },
        {
            "flag": "-V",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "-V",
            "long": null,
            "arg": null,
            "description": "ing RCS files with others who are running older versions of RCS. To see which version of RCS your correspondents are running, have them invoke rcs -V; this works with newer versions of RCS. If it doesn't work, have them invoke rlog on an RCS file; if none of the first few lines of output contain the string branch: it is version 3; if the dates' years have just two digits, it is version 4; otherwise, it is version 5. An RCS file generated while emulating version 3 loses its default branch. An RCS revi‐ sion generated while emulating version 4 or earlier has a time stamp that is off by up to 13 hours. A revision extracted while emulating version 4 or earlier contains ab‐ breviated dates of the form yy/mm/dd and can also contain different white space and line prefixes in the substitution for $Log$."
        },
        {
            "flag": "-x",
            "long": null,
            "arg": null,
            "description": "Use suffixes to characterize RCS files. See ci(1) for details."
        },
        {
            "flag": "-z",
            "long": null,
            "arg": null,
            "description": "time zone for date in the -ddate option. The zone should be empty, a numeric UTC off‐ set, or the special string LT for local time. The default is an empty zone, which uses the traditional RCS format of UTC without any time zone indication and with slashes separating the parts of the date; otherwise, times are output in ISO 8601 for‐ mat with time zone indication. For example, if local time is January 11, 1990, 8pm Pacific Standard Time, eight hours west of UTC, then the time is output as follows: option time output"
        },
        {
            "flag": "-z",
            "long": null,
            "arg": null,
            "description": "-zLT 1990-01-11 20:00:00-08 -z+05:30 1990-01-12 09:30:00+05:30 The -z option does not affect dates stored in RCS files, which are always UTC."
        }
    ],
    "examples": [],
    "see_also": [
        {
            "name": "ci",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/ci/1/json"
        },
        {
            "name": "ctime",
            "section": "3",
            "url": "https://www.chedong.com/phpMan.php/man/ctime/3/json"
        },
        {
            "name": "date",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/date/1/json"
        },
        {
            "name": "ident",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/ident/1/json"
        },
        {
            "name": "make",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/make/1/json"
        },
        {
            "name": "rcs",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/rcs/1/json"
        },
        {
            "name": "rcsclean",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/rcsclean/1/json"
        },
        {
            "name": "rcsdiff",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/rcsdiff/1/json"
        },
        {
            "name": "rcsmerge",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/rcsmerge/1/json"
        },
        {
            "name": "rlog",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/rlog/1/json"
        },
        {
            "name": "rcsfile",
            "section": "5",
            "url": "https://www.chedong.com/phpMan.php/man/rcsfile/5/json"
        },
        {
            "name": "info",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/info/1/json"
        }
    ],
    "tldr": {
        "source": "official",
        "description": "Check out RCS revisions (retrieve working files from the Revision Control System).",
        "examples": [
            {
                "description": "Check out the latest revision of a file (retrieves a read-only copy)",
                "command": "co {{path/to/file}}"
            },
            {
                "description": "Check out a file with a lock for editing",
                "command": "co -l {{path/to/file}}"
            },
            {
                "description": "Check out a specific revision of a file",
                "command": "co -r{{revision}} {{path/to/file}}"
            },
            {
                "description": "Check out a file and overwrite it if it already exists",
                "command": "co -f -l {{path/to/file}}"
            },
            {
                "description": "Print a specific revision to `stdout` without creating a file",
                "command": "co -p -r{{revision}} {{path/to/file}}"
            }
        ]
    }
}